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A/C Not Working on 1980 300SD After Complete Rebuild/Recharge

Submitted by sfinell on 14 August 2007 - 4:06am.
Replaced a/c compressor, evacuated and charged a/c, tested for leaks (found none), replaced a/c belt, replaced receiver dryer, replaced expansion valve, flushed a/c lines. I had cool air (not cold - about 60 degrees at vent) for about three days. Now the air is neither cool nor dry. With the a/c switched on at start up, I hear a squeal. Accelerating eliminates squeal and it doesn't return. Belt is tight. Everything seems to be right but, something isn't and I can't figure it out. Can anyone help me diagnose and fix this?
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Need more info

19 August 2007 - 8:18pm
Kent Bergsma
Did the AC work at all before you replaced all the components? Can you confirm that the AC compressor clutch is engaging when you turn the AC on? Do you know if your servo is cycling? (can you hear it wind down after you shut the engine off). With the AC off does the heater cycle from cold to hot? I am sure you have heard this is a very complex system that is extremely difficult to troubleshoot. Kent

A/C

21 August 2007 - 2:25pm
sfinell
The compressor engages when turned on. The temperature doesn't change when turning A/C off and on or changing the temp on the dial. I am wondering if it is the servo but, not sure at all and not familiar with troubleshooting an A/C system as complex as this one. It holds vacuum and is amply charged.

A/C in 300 SD

21 August 2007 - 5:46pm
gberger
Hello, I recently had quite the learning experience with my A/C System in my 1980 300SD. Have you checked all connections, hoses, hoses for leaks, etc. Did the rebuild shop who did your engine work recharge your R12 or R134? Sometimes people overlook to do things like this or will avoid if you do not ask for it to be done in the list of work. With the engine running and A/C switch on and button selected for AC mode does the compressor clutch engage? Do you feel the load being put on the engine? Was the A/C belt put back onto the compressor? Actually, you can go to www.w116.org website. Join the forum and there is about 1000 members worldwide who can provide you insight if you have no luck. Greg

A/C

23 August 2007 - 6:17am
sfinell
The compressor engages; there appear to be no leaks - it holds pressure; R12. I am beginning to believe it's the servo but am trying to find a way to temporarily bypass it to test that theory, so as not to spend hundreds replacing a part that's fine.